Device for stereophonic sound transmission in two channels



Sept. 13, 1949. K. DE BOER DEVICE FOR STEREOPHONIC SGUND TRANSMISSION IN TWO CHANNELS Filed April 10, 194s CHANNEL A CHANNEL 8 MANUAL CONTROL CONTROL SIGNALS Wm/Wm -El XOR/V62 05' 505/? CHANNEL A ATTORNEY Patented Sept. 13, 1949 DEVICE FOR STEREOPHONIC SOUND TRANSMISSION IN TWO CHANNELS Kornelis de Boer, Eindhoven, Netherlands, as-

signor, by mesne assignments, to Hartford National Bank, and Trust Company, Hartford,

Conn., as trustee Application April 10, 1946, Serial No. 660,873 In the Netherlands July 14, 1944 7 Claims.

This invention relates to an arrangement for stereophonic reproduction and more particularly to an arrangement wherein a stereophonic sound image is spread about an auditory.

The usual devices for stereophonic sound reproduction generally comprise two loudspeakers or two groups of loudspeakers spaced apart from each other and placed at one side of the auditory. The two loudspeakers or groups thereof are adapted to reproduce the high tones in the sound spectrum and bring about the stereophonic efiect by emitting sound vibrations that are supplied thereto with a difference in intensity and time through two separated channels. In addition to these loudspeakers one or more loudspeakers, adapted to reproduce low tones, may be placed preferably between the two firstmentioned groups of loudspeakers. They receive their oscillations from the two channels together or only from one of them. As is well known, the last-mentioned oscillations having a low frequency do not contribute to the stereophonic efiect.

In all these devices the sound image extends substantially in one plane and more particularly in the plane extending through the two loudspeakers or groups thereof for the high tones. In some cases, however, it has been founddesirable to spread the stereophonic space elTect over the whole auditory e. g. in reproducing a thunderstorm, rain or the like.

The object of this invention is to provide a device of the aforesaid kind which permits the obtainment of such a space effect. In accordance with the invention there is provided in .ad-

dition to the usual loudspeakers one or more loudspeakers which are placed at the opposing side in the auditory, each of which is connected to one of the channels and of which the degree of co-operation is variable in conjunction with the desired stereophonic space effect.

The illusion of acoustic perspective in the reproduction of certain noises, for instance a thunderstorm or the like, is largely increased thereby, since the audience may be surrounded, as it were, by the sound image.

The control of the degree of co-operation of the said loudspeakers may take place at will by hand e. g. guided by a sound effects score, or by means of different marks that are provided in a manner known per se on a sound film and to which may respond definite control devices.

In one preferred embodiment according to the invention the degree of cooperation of the individual loudspeakers is governed by devicesv reacting to electrical auxiliary oscillations havin a different character e. g. having different frequencies. These oscillations may be recorded on a sound film e. g. simultaneously with the sound vibrations. In this case, consequently, the control takes place entirely automatically.

In order that the invention may be more clearly understood and readily carried into effect it will now be described more fully with reference to the accompanying drawing, given by way of example.

Fig. 1 represents diagrammatically according to the invention.

Fig. 2 shows a possible form of construction of the circuit arrangement of this device.

Fig. 3 represents another form of construction of this circuit arrangement.

Referring now to Fig. 1, the reference numeral l designates the auditory wherein the stereophonic system is arranged. Placed at spaced positions at the front end of the auditory are loudspeakers L1 and L2 for the reproduction of the high tones in the sound spectrum and positioned intermediate loudspeakers Li and L2 is the loudspeaker L3 which is adapted to reproduce the low tones in the sound spectrum. Loudspeaker L1 is coupled to a first channel A for transmitting sound signals and including an amplifier A, and loudspeaker L2 is coupled to a second and independent channel B for transmitting sound signals and including a amplifier B. Channels A and B are associated with separate sound tracks on a movin film or with any other form of stereophonic recording means. Loudspeaker Ls may be fed by either of channels A and B or both but by way of example it is shown as being coupled to channel A. At the rear end of the auditory are placed additional loudspeakers L4 and L5 each coupled to channels A and B, respectively. To facilitate the control of sound distribution in the auditory, the degree of coupling between each of loudspeakers L1 and L4 to channel A is made variable at will. Likewise, the degree of coupling between loudspeakers L2 and L5 is made at will. Two preferred systems for accomplishing coupling control are illustrated in Figs. 2 and 3 and will be explained hereinafter. Instead of employing two loudspeakers L4 and L5 at the rear of the auditory it is also possible to use a single loudspeaker Le which may be coupled to either of channels A and B or both. By way of example, loudspeaker L6 is shown coupled to channel A. It will be seen that with the arrangement disclosed in Fig. 1 since the sound emanates stereoa device the loudspeakers L1 and L4, respectively, and

The electric currents from: 7 the amplifier A are supplied to the variable ree.

sistances II and I2 which are interposedlbetween lo the channel and operate asfattentuatorsl The; 1 adjustable tap on resistance H is mechanicallyganged to the adjustable "tap on'resi'stance I! in such manner whereby when resistance ll is 4 producers arranged at spaced positions at one end of the auditory andcoupled to the first and second channels respectively, a third sound reproducer positioned at the opposing end of said auditory and coupled to; said first' channel, and

mea'ns to vary simultaneously: and inversely the degree of coupling of said first and third reproducers to said first channel.

4. A'stereophonic system for an auditory, said system comprising first and second independent channels for transmitting stereophonic sound signals derivedatspaced positions from a com- ;mon' sound source, first and second sound reproducers each arranged to reproduce the high set at maximum value, resistance I2 is set at minimum value.

Variation of these resistances take place simultaneously, so that the sound can be distributed at will between the two loud-' speakers. Itwill be evident that the total sound output of loudspeakers L1 and Li'is-constant inasmuch as any increase in'the value of resistance ll results in' a-proportionate decrease in resistance I2. I

Another circuit arrangement for a variable coupling for loudspeakers L and L4 is shownin Fig. In this case the output ofamplifier A is equally divided and fed'to loudspeakers L1 and L4 through auxiliary-amplifiers 26 and 2i, respectively. The degree of 1 amplification of auxiliary amplifiers 26 and 2'! is automatically governed by control signals which are preferably conveyed by channel A. The'controlsignalsf-are given a-distinctive character, such as the frequencies above the audible spectrum, in order to facilitate their separation from the sound signals in the channel. It will be obvious,

however, that aseparate source of control' signal may be employed ifdesired. The arran ement is otherwise analogous to that of resistances II and I2 in Fig. 2, that is "the degree'of amplification of auxiliary amplifiers 25 and 21 is simultaneously and inversely varied so that plifiers remains constant.

Of course, a similar circuit arrangement may be used for the loudspeakers L2 and L5, unless onlyone loudspeakerLe be used instead {of L4 the totalo'utput energy of the two auxiliary amand L5.

I What Iclaimisr '1 1 A stereophonic systemfor an auditoryjsaid system comprising 'a'plurality of independent channels for transmitting stereophonic sound signals derived at spaced positions from'a common sound source, 'a plurality of sound repro 'ducers positioned in spaced-relation at one end of the auditory and coupled to the respective channels, and-at least 'one additional sound reproducer-positioned at the opposing end of said auditory and coupled to a respective channel.

2. A stereophonic system for an auditory, said system comprising two independent channels for transmitting stereophonic sound signals derived at spaced positions from a common sound source, two sound reproducers arranged at spaced positions at one end of the auditory and coupled to the respective channels, and at least one additional sound reproducer positioned at the opposing end of said auditory and coupled to arespective channel; 1 V

1 3. A stereophonic"system'foran auditory, said system comprising first and second independent channels for transmitting stereophonic sound signals derived atspaced positions from a common sound source, first and second sound refrequency range'of said signals, said first and second sound reproducers being disposed at spaced positions at one end of the auditoryand being coupled to the first and second channels respectively, a third sound reproducer arranged to reproduce the low frequency range of said signals and positioned at said oneend ofsaid auditory intermediate said first and second reproducers,

said third reproducer being coupled to atleast one of said channels; and fourth and fifth sound reproducers positioned in'spaced relation at'the opposing end of said 'audit'ory'and coupled to said first and second channels'respectively." I

5. A stereophonic system for an auditory, said system comprisin first and second independent channels for transmitting stereophonic sound signals derived at spaced positions from' 'a common sound source, first and second 'sou'ndreproducers each arranged to reproduce the high frequency range of said signals, said first and second sound reproducers being disposed at spacedpositioris. atone end of the auditory and being coupled to the first and second channels respectively, a'third sound reproducer arranged to reproduce the low frequency range of said signals and positioned at .said one end'ofsaid auditory intermediate said first and second 're producers, said third reproducer being coupled to at least one of said channels, and fourth and V fifth sound reproducers positioned inspaced re lation at the opposing endof said auditory and coupled to said first and' second channels respectively, means to vary simultaneously and inversely the degree of coupling Ofsaid first and fourth reproducers tosaid first channel, and means to vary simultaneously and inversely the degree of coupling of said second and 'fifth re.- producers to said second channel. 1 1

. '6. Astereophonic system'for'an auditoryfsaid system comprising first and second independent channels for transmitting sound Signalsderived at spaced positionsfrom-a'common'sound source, firstand second signal attenuators,'first'an'd second sound reproducers arranged {at spaced positions at one end of the auditory and coupled to said. first and second channels through said first and second attenuatorsrespectively; third and fourth signal attenuators, third and fourth sound reproducersarranged at spaced positions at-the other'end of said-auditoryand coupled to said first and second channelsthrough zsaid respectively,

first and third attenuators, and means to vary simultaneously and inversely said second'and fourth attenuators. i

ond, third and fourth sound reproducers, first, second, third and fourth control amplifiers connected to said first, second, third and fourth reproducers respectively, means to apportion equally the energy of sound signals in said first channel between said first and third amplifiers,

means to apportion equally the energy of sound said second and fourth reproducers being positioned in spaced relation at the rear end of said auditory.

KORNELIS DE BOER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,852,624 Nicolson Apr. 5, 1932 1,978,456 Goshaw Oct. 30, 1934 2,017,153 Kellogg Oct. 15, 1935 2,019,615 Maxfield Nov. 5, 1935 2,098,561 Beers Nov. 9, 1937 2,126,929 Snow Aug. 16, 1938 2,352,696 De Boer July 4, 1944 

